1. Field of the Invention
The present invention relates generally to optical measuring and testing equipment, particularly distance measuring equipment, and even more particularly to reflectors for use with such equipment as a geometrical surveying instrument.
2. Description of the Prior Art
Typical light emitting and laser emitting electronic distance measuring equipment requires the use of an appropriate reflector to return the emitted beam to the instrument for proper measurement of distance. Typically, an amplitude modulated light or laser beam is emitted from the source measuring instrument. The modulated beam strikes the reflector and is returned to the instrument. The returning modulated beam is there converted to an electrical signal. The phase relationship between the transmitted and reflective beams are then compared by the instrument. The comparison of phase relationship is then converted by the instrument into a direct read out of distance.
Several inconveniences and problems have arisen when using present state of the art electronic distance measuring equipment with prior art reflecting devices. The prior art reflecting devices generally have required that they be aimed at the distance measuring instrument so as to properly return the light or laser beam to the instrument. This requires a manipulation of the reflecting surface which is often difficult and occasionally impossible. Further, many reflecting units have a certain maximum angle of vertical tilt which is permitted, typically between 30.degree. and 45.degree. from center to upper or lower limits. Any distances to be measured which include greater vertical angles than these maximum limits become much more difficult to perform. A particularly important example of this problem arises where it is desired to measure the depth of a rather deep narrow depression such as a trench. The vertical angle limits placed on certain prior art devices all but prevent this measurement from being performed.
Another problem encountered in prior art devices, particularly when used in geometrical surveying is the measurement of intermediate positions between the top and bottom of steep grades including cliffs. Where the grade is too steep, it is not possible for a person to position a rod or conventional reflecting device in certain spots without risking life and limb. While it is possible to calculate the distances to these intermediate positions by a series of triangulation methods, these measurements become very tedious and time consuming.
It is therefore a primary object of the present invention to construct a reflecting device with such a shape as to eliminate the present problem of having to aim the reflector back toward the light emitting distance measuring equipment. A further object is to construct such a device such that it can be employed in the measurement of angles with any horizontal or vertical angle. It is a further object of the present invention to construct a reflecting device which can be easily lowered down into deep narrow depressions or down steep grades to any intermediate point desired. It is further an object of the present invention to provide appropriate protection for the reflective surface to prevent abrasion damage which would degrade the quality of the return signal to the light emitting electronic distance measuring equipment.